Electric compressor and method of assembling the same

ABSTRACT

An electric compressor includes a gas compression mechanism accommodated in a compressor housing and an electric motor for driving the compression mechanism. A circuit cover is joined to the outer surface of the compressor housing. The compressor housing and the circuit cover define an accommodating space. A motor driving circuit or driving the electric motor is accommodated in the accommodating space. The motor driving circuit is attached to the circuit cover. Accordingly, the compressor reduces manufacturing costs.

BACKGROUND OF THE INVENTION

The present invention relates to an electric compressor used in, forexample, a vehicle air conditioner and a method of assembling thiselectric compressor.

An electric compressor of this kind comprises an inverter for driving anelectric motor, which is mounted on a surface of a compressor housing,and a circuit cover covering the inverter (for example, JapaneseLaid-Open Utility Model No. 62-12471). Specifically, the technique inthis publication employs an assembly procedure of mounting the inverteron the surface of the compressor housing and then fixedly joining thecircuit cover to the compressor housing to cover the inverter.

However, the inverter must be handled gently and carefully partlybecause electric parts and a circuit board have low impact resistance.Accordingly, in terms of the configuration and flow of a productionline, the inverter is not compatible with the process of assembling themechanical components of the electric compressor, with which process themechanical components do not need to be handled as delicately as theinverter. Therefore, to carefully and reliably mount the inverter on thecompressor housing, it is necessary to, for example, execute thisprocess on a line separate from a line on which a process of assemblingmechanism components is executed. However, in this case, the compressorhousing, a large-sized component, must be moved between the lines. Thisrequires much labor and time. Thus disadvantageously, the manufacturingcosts of the electric compressor increase.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electriccompressor that reduces manufacturing costs as well as a method ofassembling the electric compressor.

To achieve the above-mentioned objective, the present invention providesan electric compressor. The compressor includes a compressor housing, agas compression mechanism accommodated in the compressor housing, anelectric motor that drives the compression mechanism, a motor drivingcircuit that drives the electric motor, and a circuit cover. The circuitcover is attached to an outer surface of the compressor housing. Thecompressor housing and the circuit cover define an accommodating space.The motor driving circuit is accommodated in the accommodating space.The motor driving circuit is attached to the circuit cover.

According to another aspect of the present invention, there is alsoprovided a method of assembling an electric compressor having acompression mechanism accommodated in a compressor housing. Thecompression mechanism is driven by an electric motor to compress gas.The method includes steps of attaching a motor driving circuit fordriving the electric motor to a circuit cover, and joining the circuitcover, to which the motor driving circuit is attached, to an outersurface of the compressor housing such that the compressor housing andthe circuit cover define an accommodating space for accommodating themotor driving circuit.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a vertical cross-sectional view of an electric compressor;

FIG. 2 is a side view of the electric compressor;

FIG. 3 is a cross-sectional view of FIG. 2 taken along line 1-1 in FIG.2 and showing that a rotary shaft and an electric motor have beenremoved;

FIG. 4 is an exploded view illustrating a method of assembling theelectric compressor; and

FIG. 5 is an exploded view of an electric compressor showing a secondembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electric compressor and a method of assembling the electriccompressor according to first and second embodiment of the presentinvention will now be described. The electric compressor constitutes apart of a refrigeration circuit of a vehicle air conditioner. In thesecond embodiment, description will be given only of a differencebetween the first embodiment and the second embodiment. The same orcorresponding components are denoted by the same reference numerals, andtheir description is omitted.

As shown in FIGS. 1 and 2, a compressor housing 11 constituting thecontour of an electric compressor 10 according to the first embodimentis composed of a first housing member 21 and a second housing member 22.The first housing member 21 is shaped generally like a cylinder having abottom formed on a left side of a peripheral wall 23, as viewed in thefigures. The first housing member 21 is made by die casting an aluminumalloy. The second housing member 22 is shaped like a covered cylinderforming a cover on the right of the figures. The second housing member22 is made by die casting an aluminum alloy. A closed space 24 is formedin the compressor housing 11 by fixedly joining the first housing member21 and the second housing member 22 to each other.

As shown in FIG. 1, a rotary shaft 27 is rotatably supported by thefirst housing member 21 in the closed space 24 of the compressor housing11. A rotation central axis L of the rotary shaft 27 constitutes acentral axis L of the electric compressor 10. The peripheral wall 23 ofthe first housing member 21 is arranged so as to surround the centralaxis L of the electric compressor 10.

An electric motor 12 and a compression mechanism 14 are accommodated inthe closed space 24 of the compressor housing 11. The electric motor 12is composed of a stator 12 a fixed to the inner surface of theperipheral wall 23 of the first housing member 21 and a rotor 12 bprovided inside the stator 12 a and around the rotary shaft 27. Theelectric motor 12 rotates the rotary shaft 27 by allowing the stator 12a to receive a power supply.

The compression mechanism 14 is of a scroll type comprising a fixedscroll member 14 a and a movable scroll member 14 b. In the compressionmechanism 14, the movable scroll member 14 b orbits relative to thefixed scroll member 14 a in response to rotation of the rotary shaft 27to compress a refrigerant gas. Accordingly, when the compressionmechanism 14 is driven by the electric motor 12, a low-temperature andlow-pressure refrigerant gas from an external refrigerant circuit (notshown) is sucked into the compression mechanism 14 from a suction port31 (see FIG. 2) formed in the first housing member 21, via the electricmotor 12. The refrigerant gas sucked into the compression mechanism 14is converted into a high-temperature and high-pressure refrigerant gasby a compressing action of the compression mechanism 14. The refrigerantgas is then discharged to the external refrigerant circuit through anexhaust port 32 formed in the second housing member 22.

The refrigerant gas from the external refrigerant circuit is introducedinto the compression mechanism 14 via the electric motor 12 so that thisrelatively cool refrigerant gas cools the electric motor 12 and a motordriving circuit 41, described later.

As shown in FIGS. 2 and 3, an accommodating section 36 containing anaccommodating space 35 is projected from a part of the outer surface ofthe peripheral wall 23 of the first housing member 21. The accommodatingsection 36 is composed of a frame-like side wall portion 37 integrallyextended from the outer surface of the peripheral wall 23 and a covermember 38. The cover member 38 is fixedly joined to an end surface ofthe side wall portion 37, and is separate from the compressor housing11. The cover member 38 functions as a circuit cover. The cover member38 is fixed to the side wall portion 37 at its four corners using bolts39.

As shown in FIG. 3, a bottom surface 35 a of the accommodating space 35is constituted by the outer surface of the peripheral wall 23.Specifically, the bottom surface 35 a of the accommodating space 35 isprovided by the first housing member 21. A top surface 35 b of theaccommodating space 35 is provided by the cover member 38.

A motor driving circuit 41 for driving the electric motor 12 isaccommodated in the accommodating space 35 of the accommodating section36. The motor driving circuit 41 is composed of an inverter to supplypower to the stator 12 a of the electric motor 12 on the basis of aninstruction from an air conditioner ECU (not shown).

The motor driving circuit 41 is composed of a planar circuit board 43and plural types of electric components 44 mounted on a surface 43 a ofthe circuit board 43 which is closer to the central axis L and on anopposite surface 43 b. That is, the circuit board 43 has a first surface43 b facing the cover member 38 and a second surface 43 a located on aside opposite from the cover member 38. The reference number 44 of theseelectric components generally refers to electric components 44A to 44E,described later, and other electric components not shown in thedrawings.

The electric components 44 include well-known components constitutinginverters, that is, switching elements 44A, an electrolytic capacitor44B, a transformer 44C, a driver 44D, and a fixed resistor 44E. Thedriver 44D is an IC chip that intermittently controls the switchingelement 44A on the basis of instructions from the air conditioner ECU.

Only the electric components 44 that are lower than the switchingelements 44A (provided that the switching elements 44A are arranged onthe surface 43 b) as measured from the circuit board 43 (from thesurface 43 b) are arranged on the surface 43 b that is opposite thecentral axis L, i.e., closer to the cover member 38. The electriccomponents 44 that are lower than the switching elements 44A as measuredfrom the circuit board 43 include, for example, the driver 44D and thefixed resistor 44E.

The plurality of switching elements 44A and the electric components 44that are higher than the switching elements 44A as measured from thecircuit board 43 (from the surface 43 a) are arranged on the surface 43a of the circuit board 43, which is closer to the central axis L, i.e.opposite the top surface 35 b of the cover member 38. The electriccomponents 44 that are higher than the switching elements 44A asmeasured from the circuit board 43 include, for example, theelectrolytic capacitor 44B and the transformer 44C.

The low electric components such as the switching element 44A arearranged in a central portion of the surface 43 a of the circuit board43 which portion is close to the central axis L. The high electriccapacitors such as the electrolytic capacitor 44B and the transformer44C are arranged on both sides of the central portion of the surface 43a of the circuit board 43 which sides are further from the central axisL. This arrangement enables the motor driving circuit 41 to be installedin the compressor housing 11 so that the electric components 44 mountedon the surface 43 a of the circuit board 43 extend along the cylindricalshape of the peripheral wall 23.

Accordingly, the motor driving circuit 41 can be arranged close to thecentral axis L of the electric compressor 10 because the electriccomponents 44 extend along the cylindrical shape of the peripheral wall23. Therefore, the amount of projection of the accommodating section 36from the compressor housing 11 is reduced to miniaturize the electriccompressor 10.

A central area 35 a-1 of the bottom surface 35 a of the accommodatingspace 35 corresponds to the switching elements 44A and is constructed asa plane that is close to the cover member 38 and parallel with the topsurface 35 b. Areas of the bottom surface 35 a of the accommodatingspace 35 which areas are located at respective sides of the area 35 a-1correspond to the high electrolytic capacitor 44B and the transformer44C. Concave portions 35 a-2 are formed in these areas to accommodatethe electrolytic capacitor 44B and the transformer 44C, respectively,such that clearance exists about each of the electrolytic capacitor 44 band the transformer 44C.

The motor driving circuit 41 is fixed in the accommodating space 35because the vicinities of the switching elements 44A are tightenedbetween the first housing member 21 and the cover member 38 due to theattachment of the cover member 38 to the first housing member 21. Thetightening of the motor driving circuit 41 between the first housingmember 21 (the bottom surface 35 a of the accommodating space 35) andthe cover member 38 (top surface 35 b) causes the switching elements 44Aof the circuit 41 to be pressed against the bottom surface 35 a (area 35a-1) of the accommodating space 35 at a radiating surface 44A-1 of theswitching element 44A.

Consequently, heat is efficiently exchanged between the switchingelements 44A and the first housing member 21 (peripheral wall 23), whichis relatively cool because a sucked refrigerant gas flows inside theperipheral wall 23. This allows heat to be appropriately radiated fromthe switching element 44A to stabilize operations of the motor drivingcircuit 41.

A circuit board support member 47 made of resin is mounted on thesurface 43 b of the circuit board 43, which is opposite the central axisL, so that all the electric components 44 mounted on the surface 43 bare buried in the circuit board support member 47. Consequently, a loadimposed on the switching element 44A by the pressing of the elements 44Aagainst the bottom surface 35 a of the accommodating space 35 isreceived by the cover member 38 via the circuit board 43 and the circuitboard support member 47. Therefore, the flexure of the circuit board 43near the switching elements 44A, which is caused by the above load, isprevented by direct backup support by the circuit board support member47.

A rubber sheet (elastic member) 45 that is excellent in resilience andheat conductivity is interposed between the switching elements 44A andthe bottom surface 35 a of the accommodating space 35 (area 35 a-1).That is, the switching elements 44A is pressed against and tightlycontacted with the bottom surface 35 a of the accommodating space 35 viathe sheet 45.

Accordingly, even if, for example, a dimensional tolerance causes avariation in height from the circuit board 43 among the switchingelements 44A, the elastic deformation of the sheet 45 absorbs avariation in the absolute height of each switching element 44A and avariation in relative height among the switching elements 44A. Theswitching elements 44A can thus be pressed against and tightly contactedwith the first housing member 21 (the bottom surface 35 a of theaccommodating space 35) with an appropriate force. This allows theswitching elements 44A to more appropriately radiate heat and alsoallows the motor driving circuit 41 to be stably arranged in theaccommodating space 35.

A plurality of bolts 51 are set in the top surface 35 b (cover member38) of the accommodating space 35 at intervals. A plurality of boltthrough-holes 43 c are formed through an outer peripheral potion of thecircuit board 43 of the motor driving circuit 41 in association with thebolts 51 of the cover member 38. The bolts 51 are inserted through therespective bolt through-holes 43 c in the circuit board 43. A nut 52 isattached to the tip of each bolt 51 to lock the motor driving circuit 41on the cover member 38. That is, the motor driving circuit 41 isattached to the cover member 38 using the bolts 51 and the nuts 52. Themotor driving circuit 41 is attached to the cover member 38 before thecover member 38 is fixedly joined to the first housing member 21 (seeFIG. 4).

As is apparent from the drawings, the nuts 52, attached to therespective bolts 51, simply abut the motor driving circuit 41 againstthe cover member 38 so as to prevent the motor driving circuit 41 fromcoming off the bolts 51, i.e., coming off the cover member 38. However,the nuts 52 permit the motor driving circuit 41 to move close to thecover member 38 (top surface 35 b). The structure attaching the motordriving circuit 41 to the cover member 38 using the bolts 51 and thenuts 52 does not hinder the vicinities of the switching elements 44Afrom being tightened directly between the first housing member 21.(bottom surface 35 a) and the cover member 38 (top surface 35 b).

As shown in FIG. 4, it is important to manage the distance X from thetop surface 35 b to the radiating surface 44A-1 in the cover member 38(including the motor driving circuit 41) in order to suitably adjust aforce that tightens the motor driving circuit 41 between the firsthousing member 21 and the cover member 38, that is, a force that pressesthe switching elements 44A against the bottom surface 35 a. In thepresent embodiment, the distance X is set at a suitable value byadjusting the thickness of the circuit board support member 47 betweenthe surface 43 b of the circuit board 43 and the top surface 35 b of thecover member 38. That is, the circuit board support member 47 functionsas an adjusting member.

Specifically, before the cover member 38 is fixedly joined to the firsthousing member 21, the circuit board support member 47 is formeddirectly by depositing a resin on the surface 43 b of the circuit board43. The thickness of the circuit board support member 47 is adjusted bytightening the nuts 52 while the resin remains soft (its thickness canbe varied) to compress the resin between the motor driving circuit 41and the cover member 38, while allowing an excess amount of resin toescape to the side of the circuit board support member 47. Then, theresin hardens to determine the thickness of the circuit board supportmember 47, that is, to set the distance X at a suitable value. Then, thecover member 38 (including the motor driving circuit 41) is fixedlyjoined to the first housing member 21.

The present embodiment, configured as described above, has the followingadvantages.

(1) The motor driving circuit 41 is attached to the cover member 38.Consequently, an assembly procedure can be employed which attaches themotor driving circuit 41 to the cover member 38 and then fixedly joinsthe cover member 38 to the first housing member 21. The employment ofthis assembly procedure produces the following effects.

Even if, for example, the motor driving circuit 41 is attached to thecover member 38 on a line separate from a line on which the cover member38 is fixedly joined to the first housing member 21, the cover member 38(including the motor driving circuit 41), which is smaller than thefirst housing member 21, can be easily moved between the lines.Furthermore, the motor driving circuit 41 is reinforced by the covermember 38. Accordingly, even when the cover member 38 is fixedly joinedto the first housing member 21, it is unnecessary to give specialconsiderations as required if for example, only the motor drivingcircuit 41 is handled. Consequently, the process of fixedly joining thecover member 38 to the first housing member 21 can be easilyincorporated into an assembly line for the mechanism parts of theelectric compressor 10. Therefore, the manufacturing costs of theelectric compressor can be reduced compared to the technique in theutility model publication in the prior art section.

(2) The switching elements 44A are pressed against the first housingmember 21 by tightening the motor driving circuit 41 between the firsthousing member 21 and the cover member 38 in the accommodating space 35on the basis of the fixed joining of the cover member 38 to the firsthousing member 21. Consequently, it is unnecessary to attach theswitching elements directly to the compressor housing by bolting or thelike in order to allow the switching elements to more appropriatelyradiate heat, as described in, for example, the utility modelpublication in the prior art section. This makes it possible to attachthe motor driving circuit 41 to the cover member 38. Therefore, theabove assembly procedure can be employed, which attaches the motordriving circuit 41 to the cover member 38 and then fixedly joins thecover member 38 to the first housing member 21.

Specifically, according to the present embodiment, it is possible toreduce the manufacturing costs of the electric compressor 10 employingthe above assembly procedure and to allow the switching elements 44A tomore appropriately radiate heat by tightly contacting the switchingelements 44A with the compressor housing 11.

FIG. 5 shows the second embodiment. In the present embodiment, a spacer55 is interposed between the cover member 38 (top surface 35 b) and thecircuit board support member 47. The distance X of the cover member 38(including the motor driving circuit 41) is adjusted to a suitable valueby adjusting the thickness of the spacer 55 rather than the thickness ofthe circuit board support member 47.

In the present embodiment, first, before the attachment of the motordriving circuit 41 to the cover member 38, the thickness X1 of thevicinities of the switching elements 44A of the motor driving circuit 41is measured. The thickness X1 of the vicinities of the switchingelements 44A of the motor driving circuit 41 is the distance between thetip surface (the top surface in the figure) of the circuit board supportmember 47 and the radiating surfaces 44A-1 of the switching elements44A. Then, the spacer 55, the thickness X2 of which corresponds to thedifference between the measured value X1 and the preset suitable valueof the distance X, is selected from spacers having plural values ofthickness. Then, the selected spacer 55 is interposed between the motordriving circuit 41 (circuit board support member 47) and the covermember 38 (the top surface 35 b of the accommodating space 35).

The selection of the thickness X2 of the spacer 55 need not necessarilymeet the equation “(the suitable value of the distance X)−X1=X2”. Anysimilar value may be used and a slight error is tolerated. That is, evenif the selected spacer 55 has a thickness X2 that does not meet theabove equation, this error is absorbed by the elastic deformation of thesheet 45 to some degree.

The present embodiment has advantages similar to those of the firstembodiment. Furthermore, the distance X of the cover member 38(including the motor driving circuit 41) is adjusted to the suitablevalue by selecting the spacer 55 to have one of the already providedplural values of thickness. This eliminates the need for a cumbersomeoperation of fine-tuning the thickness of a soft resin of the circuitboard support member 47 at the site where the electric compressor 10 isassembled as in the case of the above described first embodiment.Moreover, the time required to wait for the resin to harden can be savedto reduce the time required to adjust the distance X.

The invention may be embodied in the following forms.

In the above embodiments, the bolts 51 and nuts 52 are used to attachthe motor driving circuit 41 to the cover member 38. However, thepresent invention is not limited to this aspect. The motor drivingcircuit 41 may be attached to the cover member 38 using snap engagement,an adhesive, a band, or the like.

In the above embodiments, the electric compressor 10 is embodied as whatis called a fully electric compressor in which the electric motor 12 isthe only driving source for the compression mechanism 14. However, theelectric compressor 10 may be embodied as, for example, what is called ahybrid compressor in which an engine that is a driving source for thevehicle is used as another driving source for the compression mechanism14.

The compression mechanism 14 is not limited to a scroll type. It may beof, for example, a piston type, a vane type, or a helical type.

The present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. An electric compressor, comprising: a compressor housing; a gascompression mechanism accommodated in the compressor housing; anelectric motor that drives the compression mechanism; a motor drivingcircuit that drives the electric motor; and a circuit cover attached toan outer surface of the compressor housing, wherein the compressorhousing and the circuit cover define an accommodating space, wherein themotor driving circuit is accommodated in the accommodating space, andwherein the motor driving circuit is attached to the circuit cover. 2.The compressor according to claim 1, wherein a fastener for attachingthe motor driving circuit to the circuit cover is attached to the cover,wherein the fastener prevents the motor driving circuit from beingdetached from the circuit cover, and permits the motor driving circuitto move toward the circuit cover.
 3. The compressor according to claim2, wherein the fastener includes a bolt and a nut, wherein the bolt isinserted through the motor driving circuit with a proximal end of thebolt fixed to the circuit cover, and the nut is threaded to a distal endof the bolt.
 4. The compressor according to claim 1, wherein, when thecircuit cover is joined to the compressor housing, the motor drivingcircuit is held between the compressor housing and the circuit cover. 5.The compressor according to claim 4, wherein the motor driving circuitincludes a circuit board and a switching element, wherein the circuitboard has a first surface facing the circuit cover and a second surfacelocated on a side opposite from the circuit cover, and wherein theswitching element is mounted on the second surface, and wherein, whenthe circuit cover is joined to the compressor housing, the switchingelement is pressed against the compressor housing.
 6. The compressoraccording to claim 5, wherein an adjusting member is arranged betweenthe circuit cover and the circuit board, and wherein the adjustingmember adjusts force with which the switching element is pressed againstthe compressor housing.
 7. The compressor according to claim 6, whereinthe adjusting member includes a circuit board support member, andwherein the circuit board support member is located on a part of thefirst surface of the circuit board that corresponds to the switchingelement.
 8. The compressor according to claim 7, wherein the circuitboard support member is made of resin.
 9. The compressor according toclaim 6, wherein the adjusting member includes a spacer arranged betweenthe circuit cover and the circuit board.
 10. The compressor according toclaim 9, wherein the spacer is a selected one of a plurality of spacersthat have been prepared in advance, wherein the spacers have differentthicknesses.
 11. The compressor according to claim 5, wherein an elasticmember is arranged between the compressor housing and the switchingelement.
 12. A method of assembling an electric compressor having acompression mechanism accommodated in a compressor housing, wherein thecompression mechanism is driven by an electric motor to compress gas,the method comprising: attaching a motor driving circuit for driving theelectric motor to a circuit cover; and joining the circuit cover, towhich the motor driving circuit is attached, to an outer surface of thecompressor housing such that the compressor housing and the circuitcover define an accommodating space for accommodating the motor drivingcircuit.
 13. The assembling method according to claim 12, wherein thestep of attaching the motor driving circuit to the circuit coverincludes attaching the motor driving circuit to the circuit cover with afastener such that the motor driving circuit is prevented from beingdetached from the circuit cover, and permitted to move toward thecircuit cover.
 14. The assembling method according to claim 12, wherein,when the circuit cover is joined to the compressor housing, the motordriving circuit is held between the compressor housing and the circuitcover.
 15. The assembling method according to claim 14, wherein themotor driving circuit includes a circuit board and a switching element,wherein the circuit board has a first surface facing the circuit coverand a second surface located on a side opposite from the circuit cover,and wherein the switching element is mounted on the second surface, andwherein, when the circuit cover is joined to the compressor housing, theswitching element is pressed against the compressor housing.
 16. Theassembling method according to claim 15, further comprising arranging anadjusting member between the circuit cover and the circuit board toadjust force with which the switching element is pressed against thecompressor housing.
 17. The assembling method according to claim 16,wherein the adjusting member is made of resin, the method furthercomprising: providing the resin for the adjusting member between thecircuit cover and the circuit board before the resin is hardened; andattaching the circuit board to the circuit cover while the resin remainssoft such that the thickness of the adjusting member between the circuitcover and the circuit board is adjusted.
 18. The assembling methodaccording to claim 16, wherein the step of arranging the adjustingmember includes arranging a spacer between the circuit cover and thecircuit board, wherein the spacer is selected from a plurality ofspacers having different thicknesses.